The cells in the lining of blood vessels, known as the endothelium, perform many functions, including maintaining the elasticity of blood vessels and regulating the activity of immune cells. Endothelial function is measured by detecting transient increases in blood flow, a marker known as the reactive hyperemia index. Japanese researchers enrolled a group of healthy, nondiabetic men in a study in which each was randomly assigned to consume a 75-gram glucose load with or without green coffee bean polyphenols. Blood glucose and insulin levels increased in both groups, and there were no differences between the groups; however, the reactive hyperemia index rose significantly in the polyphenol group. The researchers conclude, “These findings suggest that a single ingestion of [coffee polyphenols] improves peripheral endothelial function after glucose loading in healthy subjects.”Ochiai, Ryuji, et al. (2013). Coffee polyphenols improve peripheral endothelial function after glucose loading in healthy male adults. Nutrition Research. Published online November 18 ahead of press.
—Dr. Bob Goldman
